Alliteration
The repetition of the same or similar sounds at the beginning of words. Some famous examples of alliteration are tongue twisters such as Betty Botta bought some butter and Peter Piper picked a peck of pickled peppers.

Assonance
The repetition or a pattern of similar sounds, especially vowel sounds, as in the tongue twister "Moses supposes his toeses are roses."

Couplet
In a poem, a pair of lines that are the same length and usually rhyme and form a complete thought. Shakespearean sonnets usually end in a couplet.

Hyperbole
a figure of speech in which exceptional exaggeration is deliberately used for emphasis rather than deception. Andrew Marvell employed hyperbole throughout To His Coy Mistress:

An hundred years should go to praise
Thine eyes and on thy forehead gaze;
Two hundred to adore each breast;
But thirty thousand to the rest …

Irony,
figure of speech in which what is stated is not what is meant. The user of irony assumes that his reader or listener understands the concealed meaning of his statement. Perhaps the simplest form of irony is rhetorical irony, when, for effect, a speaker says the direct opposite of what she means. Thus, in Shakespeare's Julius Caesar, when Mark Antony refers in his funeral oration to Brutus and his fellow assassins as “honorable men” he is really saying that they are totally dishonorable and not to be trusted. Dramatic irony occurs in a play when the audience knows facts of which the characters in the play are ignorant. The most sustained example of dramatic irony is undoubtedly Sophocles' Oedipus Rex, in which Oedipus searches to find the murderer of the former king of Thebes, only to discover that it is himself, a fact the audience has known all along.

Metonymy
figure of speech in which an attribute of a thing or something closely related to it is substituted for the thing itself. Thus, “sweat” can mean “hard labor,” and “Capitol Hill” represents the U.S. Congress.

Onomatopoeia
in language, the representation of a sound by an imitation thereof; e.g., the cat mews. Poets often convey the meaning of a verse through its very sound. For example, in “Song of the Lotus-Eaters” Tennyson indicates the slow, sensuous, and langorous life of the Lotus-Eaters by the sound of the words he uses to describe the land in which they live:

Here are cool mosses deep,
And through the moss the ivies creep,
And in the stream the long-leaved flowers weep,
And from the craggy ledge the poppy hangs in sleep.

Onomatopoeia can also represent harsh and unpleasant sounds, as in Browning's “Meeting at Night”:

A tap at the pane, the quick sharp scratch
And blue spurt of a lighted match.

Simile
in rhetoric, a figure of speech in which an object is explicitly compared to another object. Robert Burns's poem “A Red Red Rose” contains two straightforward similes:

My love is like a red, red rose
That's newly sprung in June:
My love is like the melody
That's sweetly played in tune.

Free verse (also vers libre)
Poetry composed of either rhymed or unrhymed lines that have no set meter.

Limerick
A light, humorous poem of five usually anapestic lines with the rhyme scheme of aabba.